Direct cylinder injection-type spark ignition internal combustion engine

ABSTRACT

A direct cylinder injection-type spark ignition internal combustion engine is disclosed. The engine comprises a spark plug, a cavity formed in the top surface of a piston, and a fuel injection valve for injecting fuel into the cavity in nearly the shape of a fan having a relatively small thickness. When the fuel injected in nearly the shape of a fan from the fuel injection valve is considered by being divided into a plurality of fuel segments in a radial direction, a side wall of the cavity has a first fuel deflection passage  82   a  and a second fuel deflection passage  82   b  for so deflecting at least two of the plurality of fuel segments as to pass near the spark plug. The side wall of the cavity is at least partly provided with a return portion  83  that protrudes toward the inside of the cavity. The first fuel deflection passage is not provided with the return portion  83  or is provided with the return portion having a short protrusion, and the second fuel deflection passage is provided with the return portion  83  having a long protrusion.

[0001] This is a Division of application Ser. No. 09/974,054 filed Oct.11, 2001, which in turn is a Division of application Ser. No. 09/348,483filed Jul. 7, 1999 now U.S. Pat. No. 6,336,437 issued Jan. 8, 2002. Theentire disclosure of the prior applications is hereby incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a direct cylinder injection-typespark ignition internal combustion engine.

[0004] 2. Description of the Prior Art

[0005] There has heretofore been known to produce stratified chargecombustion by directly injecting the fuel into the cylinder to form amixture in the vicinity only of a spark plug at the ignition timing toburn a lean mixture in the cylinder as a whole. To carry out thestratified charge combustion, in general, the fuel injection valve isopened for only a period required for injecting a required amount offuel from a crank angle for starting the fuel injection set in thelatter half of the compression stroke. It is intended that the thusinjected fuel proceeds into a concave combustion chamber formed in thetop surface of the piston and is deflected toward the spark plug, due tothe shape of the combustion chamber, while being vaporized after robbingheat from the wall surface of the combustion chamber in order to form amixture that can be favorably ignited near the spark plug.

[0006] In general, the fuel injection valve injects fuel in a form thatis conically concentrated. Therefore, a relative long period is requiredwhile the fuel injected in the last stage of fuel injection becomes acombustible mixture utilizing the heat from the wall surface of thecombustion chamber. To ensure this period, therefore, the fuel-injectionend timing must be advanced. An amount of fuel which can be injected inthe latter half of the compression stroke, therefore, inevitablydecreases, and the stratified charge combustion must be abandoned inhigh engine load operations in which a relatively large amount of fu lis required. It has therefore been desired to carry out stratifiedcharge combustion, which is effective in decreasing the consumption offuel, over a wide range of engine operation conditions.

[0007] Japanese Unexamined Patent Publication (Kokai) No. 9-158736proposes injecting the fuel in the shape of a flat fan having arelatively small thickness by using a fuel injection valve having aninjection hole in the shape of a slit. The thus injected fuel can robheat from a wide area of the wall surface of the combustion chamber,making it possible to form a combustible mixture within a short periodand to retard the timing for ending the injection of fuel. It istherefore possible to increase an amount of fuel injected in the latterhalf of the compression stroke and to expand the region of stratifiedcharge combustion toward the high engine load side.

[0008] According to the prior art as described above, even if the timingfor ending the injection of fuel is retarded, a combustible mixture canbe reliably formed from the injected fuel at an ignition timing. Thethus formed combustible mixture has a flat shape with its length beingshorter than the width thereof and rises nearly in the direction of thelength. The ignition timing must occur while the combustible mixture isrising and is coming in contact with the spark plug. However, thecombustible mixture has a relatively short length and stays contacted tothe spark plug while it is rising for only a relative short period.Therefore, it may often happen that the combustible mixture has alreadypassed over the spark plug at the ignition timing due to a slightdeviation in the timing for forming the combustible mixture, and thereliable ignition performance is not maintained.

SUMMARY OF THE INVENTION

[0009] The object of the present invention therefore is to reliablymaintain the ignition performance and to reliably expand the region ofthe stratified charge combustion toward the high engine load side in adirect cylinder injection-type spark ignition internal combustion enginein which the fuel is injected in the form of a flat fan having arelative small thickness.

[0010] According to the present invention, there is provided a firstdirect cylinder injection-type spark ignition internal combustioncomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel into the cavity in nearlythe shape of a fan having a relatively small thickness, wherein, whenthe fuel injected in nearly the shape of a fan from the fuel injectionvalve is considered by being divided into a plurality of fuel segmentsin a radial direction, a side wall of the cavity has a first fueldeflection passage and a second fuel deflection passage for deflectingat least two of the plurality of fuel segments to pass near the sparkplug, the side wall of the cavity is at least partly provided with areturn portion that protrudes toward the inside of the cavity, the firstfuel deflection passage is not provided with the return portion or isprovided with the return portion having a short protrusion, and thesecond fuel deflection passage is provided with the return portionhaving a long protrusion.

[0011] According to the present invention, there is provided a seconddirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel into the cavity in nearlythe shape of a fan having a relatively small thickness, wherein, whenthe fuel injected in nearly the shape of a fan from the fuel injectionvalve is considered as being divided into a plurality of fuel segmentsin a radial direction, a side wall of the cavity has a first fueldeflection passage and a second fuel deflection passage for deflectingat least two of the plurality of fuel segments to pass near the sparkplug, the side wall of the cavity is at least partly provided with anarcuate portion having an arcuate shape in cross section in the verticaldirection, and a radius of curvature of the arcuate shape of saidarcuate portion on said first fuel deflection passage is larger thanthat of said arcuate portion on said second fuel deflection passage.

[0012] According to the present invention, there is provided a thirddirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel into the cavity in nearlythe shape of a fan having a relatively small thickness, wherein, whenthe fuel injected in nearly the shape of a fan from the fuel injectionvalve is considered as being divided into a plurality of fuel segmentsin a radial direction, a side wall of the cavity has a first fueldeflection passage and a second fuel deflection passage for deflectingat least two of the plurality of fuel segments to pass near the sparkplug, the side wall of the cavity is at least partly provided with areturn portion that protrudes toward the inside of the cavity, the sidewall of the cavity inclusive of the return portion has an arcuate shapein cross section in the vertical direction, the first fuel deflectionpassage is not provided with the return portion or is provided with thereturn portion having the shortest protrusion, a radius of curvature ofthe arcuate shape of the first fuel deflection passage is the greatest,and the first fuel deflection passage is closest to the spark plug.

[0013] According to the present invention, there is provided a fourthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a first fuel deflection passage and a second fueldeflection passage for deflecting at least two of the plurality of fuelsegments led by the plurality of fuel leading passages to pass near thespark plug, and the angle of collision of the fuel in a first fuelleading passage among the plurality of fuel leading passages for leadingthe fuel segment to the first fuel deflection passage, is smaller thanthe angle of collision of the fuel in a second fuel leading passageamong the plurality of fuel leading passages for leading the fuelsegment to the second fuel deflection passage.

[0014] According to the present invention, there is provided a fifthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a first fuel deflection passage and a second fueldeflection passage for d flecting at least two of the plurality of fuelsegments led by the plurality of fuel leading passages to pass near thespark plug, and the depth near the side wall of the cavity in a firstfuel leading passage among the plurality of fuel leading passages forleading the fuel segment to the first fuel deflection passage, issmaller than the depth near the side wall of said cavity in a secondfuel leading passage among the plurality of fuel leading passages forleading the fuel segment to the second fuel deflection passage.

[0015] According to the present invention, there is provided a sixthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a plurality of fuel deflection passages for deflectingall of the plurality of fuel segments led by the plurality of fuelleading passages to pass near the spark plug, and the lengths in theplurality of fuel leading passages from positions where the fuelcollides to points of a predetermined depth of the cavity graduallychange.

[0016] According to the present invention, there is provided a seventhdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a first fuel deflection passage and a second fueldeflection passage for deflecting at least two of the plurality of fuelsegments led by the plurality of fuel leading passages to pass near thespark plug, concave or convex resisting portions of a predeterminednumber are formed on at least one of the second fuel deflection passageand a second fuel leading passage among the plurality of fuel leadingpassages for leading the fuel segment to the second fuel deflectionpassage, and the resisting portions of a number smaller than thepredetermined number are formed on at least one of the first fueldeflection passage and a first fuel leading passage among the pluralityof fuel leading passages for leading the fuel segment to the first fueldeflection passage, or the resisting portions are formed on neither thefirst fuel deflection passage nor the first fuel leading passage.

[0017] According to the present invention, there is provided a eighthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a first fuel deflection passage and a second fueldeflection passage for deflecting at least two of the plurality of fuelsegments led by the plurality of fuel leading passages to pass near thespark plug, a first resisting portion of a concave shape having apredetermined depth or of a convex shape having a predetermined heightis formed on at least one of the second fuel deflection passage and asecond fuel leading passage among the plurality of fuel leading passagesfor leading the fuel segment to the second fuel deflection passage, anda second resisting portion of a concave shape having a depth smallerthan the predetermined depth or of a convex shape having a heightsmaller than the predetermined height is formed on at least one of thefirst fuel deflection passage and a first fuel leading passage among theplurality of fuel leading passages for leading the fuel segment to thefirst fuel deflection passage, or the first resisting portion is formedon neither the first fuel deflection passage nor the first fuel leadingpassage.

[0018] According to the present invention, there is provided a ninthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward th side wall of the cavity, the side wall ofthe cavity has a first fuel deflection passage and a second fueldeflection passage for deflecting at least two of the plurality of fuelsegments led by the plurality of fuel leading passages to pass near thespark plug, and a plurality of guide protuberances are formed on thebottom surface of the cavity to define a first fuel leading passageamong the plurality of fuel leading passages for leading the fuelsegment to the first fuel deflection passage and a second fuel leadingpassage among the plurality of fuel leading passages for leading thefuel segment to the second fuel deflection passage, the plurality ofguide protuberances being nearly in a linear form, and the angle ofdeflection of the fuel segment in the first fuel leading passage beingsmaller than the angle of deflection of the fuel segment in the secondfuel leading passage.

[0019] According to the present invention, there is provided a tenthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a plurality of fuel deflection passages for deflectingall of the fuel segments led by the plurality of fuel leading passagesto pass near the spark plug, and a plurality of guide protuberances areformed on the bottom surface of the cavity to define the plurality offuel leading passages, the plurality of guide protuberances being nearlyin a linear form and nearly in parallel with a plane that passes throughthe center of the injection hole of the fuel injection valve and thecenter of the cavity.

[0020] According to the present invention, there is provided a eleventhdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel in nearly the shape of afan having a relatively small thickness so that the fuel collides with abottom wall of the cavity at an acute angle, wherein, when the fuelinjected in nearly the shape of a fan from the fuel injection valve isconsidered as being divided into a plurality of fuel segments in aradial direction, the bottom wall of the cavity has a plurality ofneighboring fuel leading passages for leading the plurality of fuelsegments collided toward the side wall of the cavity, the side wall ofthe cavity has a first fuel deflection passage and a second fueldeflection passage for deflecting at least two of the plurality of fuelsegments led by the plurality of fuel leading passages to pass near thespark plug, and a plurality of guide protuberances are formed on thebottom surface of the cavity to define a first fuel leading passageamong the plurality of fuel leading passages for leading the fuelsegment to the first fuel deflection passage from a second fuel leadingpassage among the plurality of fuel leading passages for leading thefuel segment to the second fuel deflection passage, the plurality ofguide protuberances being in a curved form, and the center lines in thefirst fuel leading passage and in the second fuel guide passage definedby the plurality of guide protuberances have such shapes that a radiusof curvature of the center line of the first fuel leading passage islarger than a radius of curvature of the center line of the second fuelleading passage or the center line of the first fuel leading passage isstraight.

[0021] According to the pr sent invention, there is provided a twelfthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel into the cavity in nearlythe shape of a fan having a relatively small thickness, wherein thecavity has a side wall for deflecting all the fuel to pass near thespark plug, and a plurality of deflection guide protuberances are formedin the cavity to deflect the fuel in the direction of width thereof.

[0022] According to the present invention, there is provided athirteenth direct cylinder injection-type spark ignition internalcombustion engine comprising a spark plug, a cavity formed in the topsurface of a piston, and a fuel injection valve for injecting fuel innearly the shape of a fan having a relatively small thickness so thatthe fuel collides with a bottom wall of the cavity at an acute angle,wherein the fuel that has collided with the bottom wall of the cavitytravels toward the side wall of the cavity along the bottom wall, theside wall of the cavity deflects the whole fuel that has arrived at theside wall to pass near the spark plug, and the bottom wall of the cavityis inclined from one side end of the fuel travelling on the bottom walltoward the other side end thereof.

[0023] According to the present invention, there is provided afourteenth direct cylinder injection-type spark ignition internalcombustion engine comprising a spark plug, a cavity formed in the topsurface of a piston, and a fuel injection valve for injecting fuel innearly the shape of a fan having a relatively small thickness so thatthe fuel collides with a bottom wall of the cavity at an acute angle,wherein the fuel that has collided with the bottom wall of the cavitytravels toward the side wall of the cavity along the bottom wall, and avertical plan at the center of the side wall of th cavity in a range atwhere the fuel arrives intersects a vertical plane at the center of thefuel at a predetermined angle.

[0024] According to the present invention, there is provided a fifteenthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,a means for forming a swirl that rotates in a cylinder in nearly thehorizontal direction, and a fuel injection valve for injecting fuel intothe cavity in nearly the shape of a fan having a relatively smallthickness, wherein the cavity has a side wall for deflecting all thefuel to pass near the spark plug, and a protruding portion is formed onthe top surface of the piston corresponding to at least the side wall ofthe cavity over a range for deflecting the fuel.

[0025] According to the present invention, there is provided a sixteenthdirect cylinder injection-type spark ignition internal combustion enginecomprising a spark plug, a cavity formed in the top surface of a piston,and a fuel injection valve for injecting fuel into the cavity in nearlythe shape of a fan having a relatively small thickness, wherein thecavity has a side wall for deflecting all the fuel to pass near thespark plug, and a squish area is formed on the top surface of the pistonto generate a squish that travels chiefly in the direction of width ofthe fuel to pass near the spark plug.

[0026] According to the present invention, there is provided aseventeenth direct cylinder injection-type spark ignition internalcombustion engine comprising a spark plug, a cavity formed in the topsurface of a piston, and a fuel injection valve for injecting fuel intothe cavity in nearly the shape of a fan having a relatively smallthickness, wherein a squish area is formed on the top surface of thepiston to generate a squish that travels chiefly toward the fuelinjection valve from the side opposing the fuel injection valve to passnear the spark plug, and a plurality of stepped portions are formed inthe cavity, which portions are successively collided with by the fuelinjected from the fuel injection valve accompanying the rise of thepiston, at least two of the stepped portions which are collided with bythe fuel, when an amount of fuel injected is small, deflect the collidedfuel, in parallel, toward the upstream side of the squish beyond thespark plug.

[0027] According to the present invention, there is provided aeighteenth direct cylinder injection-type spark ignition internalcombustion engine comprising a spark plug and a fuel injection valve fordirectly injecting fuel into the cylinder, wherein the fuel injectedfrom the fuel injection valve passes near the spark plug directly orafter being deflected, and the injection rate of the fuel injectionvalve is decreased in the last stage of fuel injection.

[0028] According to the present invention, there is provided anineteenth direct cylinder injection-type spark ignition internalcombustion engine comprising a spark plug and a fuel injection valve fordirectly injecting fuel into the cylinder, wherein the fuel injectedfrom the fuel injection valve passes near the spark plug directly orafter being deflected, and a crank mechanism has the center of the crankshaft deviated from the center axis of the piston so that the angularspeed of the crank is lowered in the compression stroke.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a vertical sectional view schematically illustrating adirect cylinder injection-type spark ignition internal combustion engineaccording to a first embodiment of the present invention;

[0030]FIG. 2 is a plan view of a piston shown in FIG. 1;

[0031]FIG. 3(A) is an (A)-(A) sectional view of a side wall of a cavityin FIG. 2;

[0032]FIG. 3(B) is a (B)-(B) sectional view of the side wall of thecavity in FIG. 2;

[0033]FIG. 3(C) is a (C)-(C) sectional view of the side wall of thecavity in FIG. 2;

[0034]FIG. 4(A) is a view illustrating a behavior of the combustiblemixture according to a prior art;

[0035]FIG. 4(B) is a view illustrating a behavior of the combustiblemixture according to the first embodiment of the present invention;

[0036]FIG. 5 is a plan view of a piston corresponding to that of FIG. 2;

[0037]FIG. 6(A) is a (D)-(D) sectional view showing a side wall of acavity shown in FIG. 5, and illustrates the direct cylinderinjection-type spark ignition internal combustion engine according to asecond embodiment of the present invention;

[0038]FIG. 6(B) is an (E)-(E) sectional view of the side wall of thecavity shown in FIG. 5 in the second embodiment of the presentinvention;

[0039]FIG. 6(C) is an (F)-(F) sectional view of the side wall of thecavity shown in FIG. 5 in the second embodiment of the presentinvention;

[0040]FIG. 7(A) is a (D)-(D) sectional view showing the side wall of thecavity shown in FIG. 5, and illustrates the direct cylinderinjection-type spark ignition internal combustion engine according to athird embodiment of the present invention;

[0041]FIG. 7(B) is an (E)-(E) sectional view of the side wall of thecavity shown in FIG. 5 in the third embodiment of the present invention;

[0042]FIG. 7(C) is an (F)-(F) sectional view of the side wall of thecavity shown in FIG. 5 in the third embodiment of the present invention;

[0043]FIG. 8(A) is a (D)-(D) sectional view showing the side wall of thecavity shown in FIG. 5, and illustrates the direct cylinderinjection-type spark ignition internal combustion engine according to afourth embodiment of the present invention;

[0044]FIG. 8(B) is an (E)-(E) sectional view of the side wall of thecavity shown in FIG. 5 in the fourth embodiment of the presentinvention;

[0045]FIG. 8(C) is an (F)-(F) sectional view of the side wall of thecavity shown in FIG. 5 in the fourth embodiment of the presentinvention;

[0046]FIG. 9 is a plan view of a piston illustrating the direct cylinderinjection-type spark ignition internal combustion engine according to afifth embodiment of the present invention;

[0047]FIG. 10 is a plan view of a piston illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to a sixth embodiment of the present invention;

[0048]FIG. 11 is a plan view of a piston illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to a seventh embodiment of the present invention;

[0049]FIG. 12 is a plan view of a piston illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to an eighth embodiment of the present invention;

[0050]FIG. 13 is a sectional view along the line (G)-(G) in FIG. 5, andillustrates the direct cylinder injection-type spark ignition internalcombustion engine according to a ninth embodiment of the presentinvention;

[0051]FIG. 14 is a view illustrating another behavior of the combustiblemixture according to the eighth embodiment of the present invention;

[0052]FIG. 15 is a plan view of a piston illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to a tenth embodiment of the present invention;

[0053]FIG. 16 is a plan view of a piston illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to an eleventh embodiment of the present invention;

[0054]FIG. 17 is a plan view of a piston illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to a twelfth embodiment of the present invention;

[0055]FIG. 18 is a vertical sectional view schematically illustratingthe direct cylinder injection-type spark ignition internal combustionengine according to a thirteenth embodiment of the present invention;

[0056]FIG. 19 is a diagram of a fuel injection pattern illustrating thedirect cylinder injection-type spark ignition internal combustion engineaccording to a fourteenth embodiment of the present invention; and

[0057]FIG. 20 is a view of a crank mechanism illustrating the directcylinder injection-type spark ignition internal combustion engineaccording to a fifteenth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058]FIG. 1 is a vertical sectional view schematically illustrating adirect cylinder injection-type spark ignition internal combustion engineaccording to a first embodiment of the present invention, and FIG. 2 isa plan view of a piston shown in FIG. 1. In these drawings, referencenumeral 1 denotes an intake port and 2 denotes an exhaust port. Theintake port 1 is communicated with the interior of the cylinder throughan intake valve 3, and the exhaust port 2 is communicated with theinterior of the cylinder through an exhaust valve 4. Reference numeral 5denotes a piston, and 6 denotes a spark plug arranged at an upperportion nearly at the center of the cylinder. A fuel injection valve 7injects fuel in the shape of a fan having a relative small thickness ina manner that the center of width of the fuel is nearly in agreementwith the center of the cylinder.

[0059] In a homogeneous combustion region where a high engine output isrequired, the fuel injection valve 7 injects fuel in a required amountin the intake stroke thereby to form a homog neous mixture in thecylinder at the ignition timing. In a stratified charge combustionregion, on the other hand, the fuel injection valve 7 starts injectingthe fuel from a crank angle set for every engine operation to injectfuel in a required amount in the latter half of the compression stroke.As shown in FIG. 1, the fuel injected in the latter half of thecompression stroke proceeds into a concave cavity 8 formed in the topsurface of the piston 5, collides with a bottom wall 81 of the cavity 8and proceeds toward a side wall 82 along the bottom wall 81, and is thendeflected toward this side and up along the side wall 82 so as to bedirected to the spark plug 6. In the following description, the word“this side” means the side of the fuel injection valve.

[0060] The fuel injected by the fuel injection valve 7 is of a flat fanshape having a relative small thickness. Therefore, the fuel afterhaving collided with the bottom wall 81 of the cavity 8 travels on thebottom wall 81 and the side wall 82 of the cavity 8 while spreading inthe direction of width as represented by dots in FIG. 2, and favorablyabsorbs heat from the cavity 8 to form, within a short period, a mixture(hereinafter referred to as combustible mixture) that can be favorablyignited. To realize the stratified charge combustion, at least the fuelinjected at the last stage of fuel injection must be forming acombustible mixture at the ignition timing. Upon injecting the fuel inthe flat fan shape having a relative small thickness, it is possible toshorten the period from the end of the fuel injection to the ignitiontiming, i.e., it is allowed to retard the end of fuel injection, so thata relative large amount of fuel can be used for forming a combustiblemixture at the ignition timing.

[0061] As represented by a solid line in FIG. 4(A), the thus formedcombustible mixture has a flat shape with its length being shorter thanthe width ther of, and rises in nearly the direction of the length.Therefore, the combustibl mixture (M) stays contacted with the ignitingposition (P) of the spark plug for only a relative short period ofmoving over a distance (L1), and the ignition timing must come withinthis relative short period. Therefore, when the timing for forming thecombustible mixture is deviated even slightly due to a slight deviationin the fuel injection timing, the combustible mixture may often havepassed over the spark plug already at the ignition timing making itdifficult to reliably ensure the ignition performance.

[0062] The present invention is to solve this problem. According to theembodiment, the side wall 82 of the cavity 8 formed in the top surfaceof the piston 5 has a return portion 83 at an upper end thereof toprotrude toward the inside of the cavity 8 at least over a range atwhere the fuel arrives, exhibiting an arcuate shape of a radius ofcurvature (r1) in the horizontal direction. FIGS. 3(A)-(C) are avertical sectional view of the side wall in this range. A verticalcenter plane (N1) at the center of the side wall 82 in a range at wherethe fuel arrives intersects a vertical center plane (N2) at the centerof the fuel injected from the fuel injection valve 7 at 180 degrees;i.e., these planes are on a straight line. FIG. 3(A) is an (A)-(A)sectional view of FIG. 2, and shows a central side wall portion 82 aclosest to the spark plug located at an upper part nearly at the centerof the cylinder. The central side wall portion 82 a has an arcuate shapein cross section of a radius of curvature of (R1) inclusive of thereturn portion 83. The return portion 83 at the central side wallportion 82 a has a length of protrusion of (L1). FIG. 3(B) is a (B)-(B)sectional view of FIG. 2, and shows a right side wall portion 82 b onthe right side of the central side wall portion 82 a. The right sidewall portion 82 b has an arcuate shape in cross section of a radius ofcurvature of (R2) inclusive of the return portion 83. The return portion83 at the right side wall portion 82 b has a length of protrusion of(L2). FIG. 3(C) is a (C)-(C) sectional view of FIG. 2, and shows a leftside wall portion 82 c on the left side of the central side wall portion82 a. The left side wall portion 82 c has an arcuate shape in crosssection of a radius of curvature of (R3) inclusive of the return portion83. The return portion 83 at the left side wall portion 82 c has alength of protrusion of (L3). There exist the following relationships inthe radii of curvature of the side wall portions in the verticaldirection and in the lengths of protrusions of the return portion 83,i.e., R1>R2>R3 and L2<L2<L3.

[0063] The fuel injected into the thus constituted cavity 8 travels onthe bottom wall 81 while spreading in the direction of width of thefuel, arrives at the side wall 82, and is deflected toward the center ofwidth of the fuel due to the side wall 82 having an arcuate shape in thehorizontal direction, and is further deflected toward this side and updue to the side wall portions having arcuate shapes in cross section.For easy explanation, it is presumed that the injected fuel is dividedinto three fuel segments in the radial direction, i.e., divided into acentral fuel segment 9 a, a right fuel segment 9 b and a left fuelsegment 9 c. Then, the central fuel segment 9 a is directed by thecentral side wall portion 82 a to the spark plug 6 located at an upperportion nearly at the center of the cylinder, the right fuel segment 9 bis directed thereto by the right side wall portion 82 b, and the leftfuel segment 9 c is directed thereto by the left side wall portion 82 c.Thus, the bottom wall 81 of the cavity 8 constitutes a central fuelleading passage, a right fuel leading passage and a left fuel leadingpassage for leading the central, right and left fuel segments 9 a, 9 band 9 c to the side wall 81, and the central, right and left side wallportions 82 a, 82 b and 82 c constitute a central fuel deflectionpassage, a right fuel deflection passage and a left fuel deflectionpassage for deflecting the central, right and left fuel segments 9 a, 9b and 9 c to pass near the spark plug 6.

[0064] In each fuel deflection passage, the shorter the length ofprotrusion of the return portion 83 is, the shorter the length of thepassage for passing the fuel becomes and, hence, the smaller theresistance of passage for passing the fuel becomes. In each fueldeflection passage, furthermore, the larger the radius of curvature ofthe arcuate shape in cross section is, the shorter the length of thepassage for passing the fuel becomes and, hence, the smaller theresistance of passage for passing the fuel becomes, irrespective ofwhether the side wall portions have generally an arcuate shape as in thepresent embodiment or partly an arcuate shape in cross section in thevertical direction. In the present embodiment, therefore, the length ofprotrusion of the return portion 83 and the radius of curvature in thearcuate shape in cross section differ as described above in the fueldeflection passages, so that the central fuel segment 9 a passing on thecentral fuel deflection passag 9 a leaves from the cavity 8 at theearliest timing and heads to the spark plug 6 at the highest speed. Theright fuel segment 9 b passing on the right fuel deflection passageleaves from the cavity 8 at the second earliest timing and heads to thespark plug 6 at the second highest speed. The left fuel segment 9 cpassing on the left fuel deflection passage leaves from the cavity 8 atthe last timing and heads to the spark plug 6 at the lowest speed.

[0065] As shown in FIG. 4(B), therefore, the combustible mixture 9 a′formed by the central fuel segment 9 a arrives at the vicinity of thespark plug 6 at the earliest timing, the combustible mixture 9 b′ formedby the right fuel segment 9 b arrives at the vicinity of the spark plug6 next, and the combustible mixture 9 c′ formed by the left fuel segment9 c arrives at the vicinity of the spark plug 6 last. These combustiblemixtures are formed by the fuel that is continuously spreading, and donot exist completely independent from each other but are overlapped andlinked at their peripheral portions as shown in FIG. 4(B).

[0066] Thus, according to the present embodiment, when the fuel injectedfrom the fuel injection valve in nearly the shape of a fan having arelative small thickness is considered as being divided into a pluralityof fuel segments in a radial direction, the combustible mixtures formedby the plurality of fuel segments are permitted to pass continuouslynear the spark plug 6 in a linked manner. That is, in the presentembodiment, the ignition timing may extend from when the combustiblemixture 9 a′ formed by the central fuel segment 9 a starts contacting tothe igniting position (P) (indicated by a solid line in FIG. 4(B)) untilthe combustible mixture 9 c′ formed by the left fuel segment 9 c isstill contacting to the igniting position (P) (indicated by a dottedline in FIG. 4(B)). In other words, the ignition may be executed whilethe combustible mixture 9 c′ formed by the left fuel segment 9 c thatarrives at the spark plug 6 last, is moving over the distance (L2).

[0067] As described above, the moving speed of the combustible mixture 9c′ becomes slow, i.e., becomes slower than the moving speed of thecombustible mixture according to the prior art shown in FIG. 4(A).Besides, the distance (L2) is sufficiently longer than theabove-mentioned distance (L1). According to the present embodiment,therefore, the combustible mixture stays contacted to the ignitingposition (P) for a relatively long period. Despite the timing forforming the combustible mixture being slightly deviated due to a slightdeviation in the fuel injection timing, therefore, it is not likely thatthe combustible mixture will have passed over the spark plug already atthe ignition timing, and thus the reliable ignition performance can beensured.

[0068] In the present embodiment and some of the embodiments that willbe described below, it is explained that the fuel injected in nearly theshape of a fan is divided into three fuel segments. However, theignition performance can be obviously improved if the injected fuel isdivided into at least two fuel segments and if the combustible mixturesformed by these fuel segments are allowed to successively pass near thespark plug. The combustible mixtures formed by the plurality of fuelsegments need not all pass near the spark plug, but the combustiblemixtures formed by at least two fuel segments may successively pass nearthe spark plug.

[0069] In the central side wall portion 82 a, the right side wall porion82 b and the left side wall portion 82 c, furthermore, at least one ofthe radius of curvature of the arcuate shape in cross section and thelength of protrusion of the return portion 83 may be continuouslychanged as shown in FIG. 2. This, in other words, means that the fuelinjected in nearly the shape of a fan is divided into very many fuelsegments and the combustible mixtures formed by these fuel segments cansuccessively pass near the spark plug 6, and thus the combustiblemixtures formed by the fuel segments are favorably linked and thepropagation of flame can be very favorably improved. In the presentembodiment, inclusive of some of the embodiments that will be describedbelow, furthermore, the passage of the fuel segment for forming thecombustible mixture that arrives first at the spark plug 6 is locatedclosest to the spark plug 6, so that the combustible mixture is allowedto arrive at the spark plug 6 at an early timing. This makes it possibleto further lengthen the period in which the combustible mixture stayscontacted to the spark plug and, hence, to ensure more reliable ignitionperformance.

[0070]FIG. 5 is a plan view of a piston corresponding to the pistonshown in FIG. 2, and illustrates the direct cylinder injection-typespark ignition internal combustion engine according to a secondembodiment of the present invention. A cavity 8′ formed in the topsurface of the piston 5′ in the present embodiment has the same shape asthe cavity 8 formed in the top surface of the piston 5 of the firstembodiment except for the points described below. A side wall 82′ of thecavity 8′ has a return portion 83′ at an upper end thereof at least overa range at where the fuel arrives, and the length of protrusion of thereturn portion 83′ is the same at any position. FIG. 6(A) is a (D)-(D)sectional view of FIG. 5, FIG. 6(B) is an (E)-(E) sectional view of FIG.5, and FIG. 6(C) is an (F)-(F) sectional view of FIG. 5. As shown inthese drawings, the side wall 82′ of the cavity 8′ has a partly arcuateshape in cross section of the same radius of curvature (R4) at leastover a range where the fuel arrives. Therefore, the central, right andleft fuel deflection passages for deflecting the fuel segments towardthe spark plug 6, have nearly the same length of passage and nearly thesame resistance to passage. As shown in FIGS. 6(A)-(C), however, theangle of inclination is different among the central fuel leading passage81 a, right fuel leading passage 81 b and left fuel leading passage 81 cat a position where the fuel collides. The central fuel leading passage81 a has the smallest angle (TH1) of collision of fuel, the right fuelleading passage 81 b has the next small angle (TH2) of collision offuel, and the left fuel leading passage 81 c has the largest angle (TH3)of collision of fuel.

[0071] When the fuel collides with these fuel leading passages,therefore, the central fuel segment 9 a loses the energy least, theright fuel segment 9 b loses energy next least, and the left fuelsegment 9 c loses energy most. Thus, as in the first embodiment, thecombustible mixture formed by the central fuel segment 9 a arrives atthe spark plug 6 earliest, the combustible gas formed by the right fuelsegment 9 b arrives at the spark plug 6 next, and the combustiblemixture formed by the left fuel segment 9 c arrives at the spark plug 6last. Therefore, the same effects as described above can be obtained. Inthe cavity 8′ in the present embodiment, the depth (H1) is nearly thesame in the vicinity of the side wall in each fuel leading passage, andthe depth (H4) is nearly the same at the start point of inclination onwhere the fuel collides. On the bottom wall of the cavity 8′, it is alsoallowable to gradually change the angle of inclination of each fuelleading passage. As in the above-mentioned embodiment, therefore,favorably linked combustible mixtures are formed and thus a favorablestratified charge combustion can be realized.

[0072]FIG. 7 is a view corresponding to FIG. 6, and illustrates thedirect cylinder injection-type spark ignition internal combustion engineaccording to a third embodiment of the present invention. Describedbelow are only differences from the second embodiment. FIG. 7(A) is a(D)-(D) sectional view of FIG. 5, FIG. 7(B) is an (E)-(E) sectional viewof FIG. 5, and FIG. 7(C) is a (F)-(F) sectional view of FIG. 5. As shownin these drawings, the angles of inclination are different among thecentral fuel leading passage 81′, right fuel leading passage 81 b′ andleft fuel leading passage 81 c′ at positions where the fuel collides.The central fuel leading passage 81 a′ has the smallest angle (TH1) ofcollision of fuel, the right fuel leading passage 81 b has the secondsmallest angle (TH4) of collision of fuel, and the left fuel guidepassage 81 c′ has the largest angle (TH5) of collision of fuel.

[0073] When the fuel collides with these fuel leading passages,therefore, the central fuel segment 9 a loses the energy least, theright fuel segment 9 b loses energy next least, and the left fuelsegment 9 c loses energy most. It is thus allowed to obtain the effectsame as that of the second embodimnt. In the cavity in the presentembodiment, th depth (H1) is nearly the same in the vicinity of the sidewall in each fuel leading passage, but the depth (H4) is the smallest atthe start point of inclination on where the fuel collides on the centralfuel leading passage 81 a′, the depth (H5) is the second smallest at thestart point of inclination on where the fuel collides on the right fuelleading passage 81 b′, and the depth (H6) is the greatest at the startpoint of inclination on where the fuel collides on the left fuel leadingpassage 81 c′. On the bottom wall of the cavity, it is also allowable togradually change the angle of inclination of each fuel leading passage.Like in the above-mentioned embodiment, therefore, favorably linkedcombustible mixtures are formed and thus a favorable stratified chargecombustion can be realized.

[0074]FIG. 8 is a view corresponding to FIG. 6, and illustrates thedirect cylinder injection-type spark ignition internal combustion engineaccording to a fourth embodiment of the present invention. Describedbelow are only differences from the second embodiment. FIG. 8(A) is a(D)-(D) sectional view of FIG. 5, FIG. 8(B) is an (E)-(E) sectional viewof FIG. 5, and FIG. 8(C) is a (F)-(F) sectional view of FIG. 5. As shownin these drawings, the angles of inclination are nearly the same amongthe fuel leading passages at positions where the fuel collides. Here,however, the depth (H1) is the smallest near the side wall in thecentral fuel leading passage 81 a″, the depth (H2) is the secondsmallest near the side wall in the right fuel leading passage 81 b″, andthe depth (H3) is the largest near the side wall in the left fuelleading passage 81 c″.

[0075] Therefore, the central fuel leading passage 81 a″ is theshortest, the right fuel leading passage 81 b″ is the second shortest,and the left fuel leading passage 81 c″ is the longest. As in the firstembodiment, therefore, the combustible mixture formed by the centralfuel segment 9 a arrives at the spark plug 6 earliest, the combustiblemixture formed by the right fuel segment 9 b arrives at th spark plug 6next earliest, and the combustible mixture formed by the left fuelsegment 9 c arrives at the spark plug 6 last, to accomplish the effectsame as the one mentioned above. In the present embodiment, too, thedepth near the side wall in the fuel leading passages may be graduallychanged to form favorably linked combustible mixtures.

[0076]FIG. 9 is a plan view of a piston corresponding to FIG. 5, andillustrates the direct cylinder injection-type spark ignition internalcombustion engine according to a fifth embodiment of the presentinvention. A cavity 8″ formed in the top surface of the piston 5″according to the present embodiment has the same shape as the cavity 8′formed in the top surface of the piston 5′ of the second embodimentexcept the points described below. In the present embodiment, the anglesof inclination are nearly the same among the fuel leading passages atpositions on where the fuel collides. Here, however, a convex resistingportion 10 is formed on the central fuel leading passage which portionextends in the direction of width of the central fuel segment. Twoconvex resisting portions 10 are formed on the right fuel leadingpassage, which portions extend in the direction of width of the rightfuel segment. Three convex resisting portions 10 are formed on the leftfuel leading passage, which portions extend in the direction of width ofthe left fuel segment.

[0077] Depending upon the number of convex resisting portions on thefuel leading passages, therefore, the central fuel leading passage hasthe smallest resistance of passage, the right fuel leading passage hasthe second smallest resistance of passage, and the left fuel leadingpassage has the largest resistance of passage. As in the firstembodiment, therefore, the combustible mixture formed by the centralfuel segment 9 a arrives at the spark plug 6 earliest, the combustiblemixture formed by the right fuel segment 9 b arrives at the spark plug 6next earliest, and the combustible mixture formed by the left fuelsegment 9 c arrives at the spark plug 6 last, to accomplish the effectsame as the one described above.

[0078] In the present embodiment, the convex resisting portions areformed on the fuel leading passages. Based on the same idea, however,the convex resistance portion may be formed on the fuel deflectionpassages. The resistance of passage can similarly be increased even byforming the resisting portions in a concave manner instead of convexmanner. Instead of or in addition to varying the number of the convex orconcave resisting portions, the height or depth of the convex or concaveresisting portions may differ vary the resistance of passage in the fuelleading passages. No resisting portion may be formed on the fuel leadingpassage or on the fuel deflection passage that should have the smallestresistance of passage.

[0079]FIG. 10 is a plan view of a piston corresponding to the pistonshown in FIG. 5, and illustrates the direct cylinder injection-typespark ignition internal combustion engine according to a sixthembodiment of the present invention. A cavity 800 formed in the topsurface of the piston 500 according to the present embodiment has thesame shape as the cavity 8′ formed in the top surface of the piston 5′of the second embodiment except the points described below. In thepresent embodiment, the bottom wall of the cavity 800 is provided withfour guide protuberances 20 for defining the central, right and leftfuel leading passages. The guide protuberances 20 are nearly in paralleland are nearly symmetrical with respect to the vertical center plane(N2) at the center of the fuel. The thus defined central fuel leadingpassage leads the central fuel segment to the central fuel deflectionpassage almost without deflecting it. However, the right and left fuelleading passages lead the right and left fuel segments to the right andleft fuel deflection passages by deflecting them in the horizontaldirection, and impart r sistance to passage of the right and left fuelsegments.

[0080] In the side wall of the cavity 800, the arc in the horizontaldirection over a range at where the fuel arrives has a radius ofcurvature (r2) smaller than the radius of curvature (r1) of the cavity8′ of the second embodiment, whereby the right and left fuel deflectionpassages work to favorably defect the fuel, that is deflected in thehorizontal direction by the right and left fuel leading passages, towardthe spark plug 6. Thus, the combustible mixture formed by the centralfuel segment arrives at the spark plug 6 earliest, and the combustiblemixtures formed by the right and left fuel segments arrive at the sparkplug 6 next earliest, contributing to extending the period in which thecombustible mixtures stay contacted to the spark plug to accomplish theeffect same as the one described above.

[0081] In the present embodiment, the right and left fuel leadingpassages have nearly the same resistance to passage, and the combustiblemixtures formed by the right and left fuel segments arrive at the sparkplug 6 nearly simultaneously. Upone tilting the guide protuberancedefining, for example, the left fuel leading passage toward the verticalcenter plane at the center of the fuel, however, the left fuel segmentis deflected in an increased degree in the horizontal direction, and theresistance to passage through the left fuel leading passage can beincreased compared with that through the right fuel leading passage,enabling the combustible mixtures formed by the fuel segments tosuccessively pass near the spark plug.

[0082]FIG. 11 is a plan view of a piston corresponding to the pistonshown in FIG. 10, and illustrates the direct cylinder injection-typespark ignition internal combustion engine according to a seventhembodiment of the present invention. A cavity 801 formed in the topsurface of the piston 501 according to the present embodiment has thesame shape as the cavity 800 formed in the top surface of the piston 500of the sixth embodiment except the points described below. In thepresent embodiment, the bottom wall of the cavity 801 is provided withfour guide protuberances 21 for defining the central, right and leftfuel leading passages. The guide protuberances 20 are curved inward withrespect to the vertical center plane (N2) at the center of the fuel andare nearly symmetrical with respect to the vertical center plane (N2) atthe center of the fuel. The farther the guide protuberance is from thevertical center plane (N2) at the center of the fuel, the smaller radiusof curvature it has. The thus defined central fuel leading passage leadsthe central fuel segment to the central fuel deflection passage almostwithout deflecting it. However, the right and left fuel leading passageslead the right and left fuel segments to the right and left fueldeflection passages by deflecting them in the horizontal direction, andimpart resistance of passage to the right and left fuel segments, makingit possible to lengthen the period in which the combustible mixturesstay contacted to the spark plugs in the same manner as in the sixthembodiment to obtain the same effect as the one described above. In thepresent embodiment, too, the resistance of passage may be differedbetween the right fuel leading passage and the left fuel leading passagebased on the same idea as in the sixth embodiment, so that thecombustible mixtures formed by the fuel segments successively pass nearthe spark plug.

[0083]FIG. 12 is a plan view of a piston corresponding to the pistonshown in FIG. 5, and illustrates the direct cylinder injection-typespark ignition internal combustion engine according to an eighthembodiment of the present invention. A cavity 802 formed in the topsurface of the piston 502 of the present embodiment has the same shapeas the cavity 8′ formed in the top surface of the piston 5′ of the scond embodiment except for the points described below. In the presentembodiment, the bottom wall of the cavity 802 has nearly the same angleof inclination at positions where the fuel collides, and is providedwith a plurality of deflection guide protuberances 22 for deflecting allthe fuel injected in nearly the form of a fan toward the left in thedirection of width of the fuel. The deflection guide protuberances 22located on the deflecting side, i.e., on the left side are tilted lessthan the deflection guide protuberances 22 located on the right side.The spark plug 6′ is slightly deflected toward the left side.

[0084] As the fuel deflected by the deflection guide protuberances 22 isfurther deflected toward this side and up by the side wall of the cavity802, the combustible mixture formed by the deflected fuel moves aslantfrom the right lower side toward the left upper side as viewed on aplane with respect to the spark plug 6 that is deflected toward the leftside as shown in FIG. 14 that corresponds to FIG. 4(A). The moving speedof the combustible mixture (M) is determined by the kinetic energypossessed by the injected fuel, and is considered to be nearly the samebetween the conventional case shown in FIG. 4(A) and the case of thepresent embodiment shown in FIG. 14. According to the present embodimentas described above, the combustible mixture (M) is contacting to theigniting position (P) while the combustible mixture (M) is moving overthe distance (L3). Since the distance (L3) is much longer than theabove-mentioned distance (L1), reliable ignition is ensured at theignition timing despite of a slight deviation in the timing for formingthe combustible mixture caused by a slight deviation in the fuelinjection timing.

[0085] In the present embodiment, the deflection guide protuberance 22located on the left side is tilted less than the deflection guideprotuberance 22 located on the right side. On the bottom wall of thecavity 802, therefore, the left side of the fuel is not so muchdeflected toward the left. Since the left side of the combustiblemixture slowly moves toward the left side, therefore, the combustiblemixture hardly comes into contact with the cylinder bore. It is thusmade possible to prevent the occurrence of a problem in that the engineoil is diluted with fuel that adheres to the cylinder bore.

[0086] In the present embodiment, the deflection guide protuberances 22are formed on the bottom wall of the cavity, i.e., on the fuel leadingpassages. However, the deflection guide protuberances 22 may be formedon the side wall of the cavity, i.e., on the fuel deflection passages.In this case, the fuel deflection passages deflect the fuel not onlytoward this side and up but also deflect the fuel toward the left in thedirection of width of the fuel. In the present embodiment and theembodiments that will be described below, the spark plug may be disposednearly at the center of the cylinder. In this case, the motion of thecombustible mixture toward the upper aslant direction approaches thevertical direction. Here, the combustible mixture stays contacted to theigniting position while it moves over a distance longer than thedistance of the prior art, and the period in which the combustiblemixture stays contacted to the spark plug is extended, making itpossible to reliably ensure the ignition performance at the ignitiontiming.

[0087]FIG. 13 is a view corresponding to (G)-(G) sectional view of FIG.5, and illustrates the direct cylinder injection-type spark ignitioninternal combustion engine according to a ninth embodiment of thepresent invention. According to the present embodiment, the bottom wallof the cavity 803 is inclined from the right side end of fuel toward theleft side end thereof. Therefore, the leftward deflecting force acts onthe fuel traveling on the bottom wall, whereby the combustible mixturemoves as shown in FIG. 14 and, as in the eighth embodiment, the periodis lengthened in which the combustible mixture stays contacted to thespark plug, and reliable ignition performance is ensured at the ignitiontiming.

[0088] In the present embodiment, the angle of inclination on the bottomwall of the cavity 803 is smaller at the left side end of the fuel thanat the right side end of the fuel, so that the left side of the fuel isnot strongly deflected toward the left on the bottom wall of the cavity803. Therefore, the left side of the combustible mixture slowly movestoward the left side and the combustible mixture hardly comes intocontact with the cylinder bore. This prevents such a problem that theengine oil is diluted with fuel that adheres on the cylinder bore.

[0089]FIG. 15 is a plan view of a piston corresponding to FIG. 2, andillustrates a direct cylinder injection-type spark ignition internalcombustion engine according to a tenth embodiment of the presentinvention. A cavity 804 formed in the top surface of the piston 504according to the present embodiment has the same shape as the cavity 8formed in the top surface of the piston 5 of the first embodiment exceptthe points described below, and is turned by a predetermined angle inthe clockwise direction about the axis in the vertical direction. In thepresent embodiment, a vertical center plane (N1′) at the center of theside wall in the range at where the fuel arrives intersects a verticalcenter plane (N2) at the center of the fuel injected from the fuelinjection valve 7 at a predetermined obtuse angle (TH), and the sparkplug 6′ is slightly deviated toward the left direction.

[0090] The thus constituted side wall deflects the fuel upward along thevertical center plane (N1′) at the center. If viewed from the spark plug6′, therefore, the combustible mixture formed by the fuel moves leftwardas it rises. Like in the eighth embodiment, therefore, the combustiblemixture moves as shown in FIG. 14, whereby th combustible mixture stayscontacted to the spark plug for an extended period making it possible toreliably ensure the ignition performance at the ignition timing.

[0091] As for the sectional shape of the side wall in the verticaldirection over a range at where the fuel arrives according to thepresent embodiment, the (J)-(J) section of the left side corresponds toFIG. 3(C), the (I)-(I) section at the center corresponds to FIG. 3(B),and the (H)-(H) section of the right side corresponds to FIG. 3(A).Therefore, the rising speed becomes slow toward the left side of thefuel and, at the ignition timing, the moving amount of this portiontoward the left with respect to the spark plug 6′ decreases. Thus, thecombustible mixture hardly comes into contact with the cylinder bore. Inthe present embodiment, the range of the side wall at where the fuelarrive is of an arcuate shape having a radius of curvature in thehorizontal direction. Upon forming the left side porion of the side wallof this range to partly have a small radius of curvature, however, themoving speed of the left side of the fuel toward the left can be loweredto more reliably prevent the combustible mixture from coming intocontact with the cylinder bore.

[0092]FIG. 16 is a plan view of a piston and illustrates the directcylinder injection-type spark ignition internal combustion engineaccording to an eleventh embodiment of the present invention. A cavity805 formed in the upper surface of the piston 505 according to thepresent embodiment deflects the fuel that is injected in the shape of aflat fan having a relatively small thickness toward this side andupside. The spark plug 6′ is deviated toward the left side. In thepresent embodiment, the intake port is so constituted as to form acounterclockwise swirl in the cylinder in the horizontal direction.Furthermore, a protruding portion 50 is formed on the top surface of thepiston 505 to correspond to the side wall of the cavity 805 over a rangeat where the fuel arrives.

[0093] Therefore, a part of the swirl turns along the protruding portionand causes the combustible mixture formed by fuel which is deflectedtoward this side and upside to move toward the left. As in the eighthembodiment, therefore, the combustible mixture moves as shown in FIG.14, whereby the combustible mixture stays contacted to the spark plugfor an extended period making it possible to reliably ensure theignition performance at the ignition timing.

[0094]FIG. 17 is a plan view of a piston and illustrates the directcylinder injection-type spark ignition internal combustion engineaccording to a twelfth embodiment of the present invention. A cavity 806formed in the upper surface of the piston 506 according to the presentembodiment deflects the fuel that is injected in the shape of a flat fanhaving a relatively small thickness toward this side and upside. Thespark plug 6′ is slightly deviated toward the left side. In the presentembodiment, a squish area 60 is formed in the top surface of the piston506 to generate a squish that moves toward the left chiefly along theside wall of the cavity 806 over a range at where the fuel arrives.

[0095] Therefore, the squish makes the combustible mixture formed by thefuel which is deflected toward this side and up, move toward the left.As in the eighth embodiment, therefore, the combustible mixture moves asshown in FIG. 14, whereby the combustible mixture stays contacted to thespark plug for an extended period making it possible to reliably ensurethe ignition performance at the ignition timing.

[0096]FIG. 18 is a vertical sectional view schematically illustratingthe direct cylinder injection-type spark ignition internal combustionengine according to a thirteenth embodiment of the present invention.Described below are only the differences from the first embodiment ofFIG. 1. On the bottom wall of th cavity 807 according to the presentembodiment, there are formed first, second and third stepp d portions807 a, 807 b and 807 c with which will be successively collided with bythe fuel injected from the fuel injection valve 7 accompanying the riseof the piston 507. In the top surface of the piston 507 is furtherformed a squish area 70 for generating a squish that travels toward thefuel injection valve from the side opposite to the fuel injection valve7.

[0097] Even under the condition where the fuel is injected in a smallamount on the low engine load side, the fuel injected from the fuelinjection valve necessarily collides with the first and second steppedportions 807 a and 807 b. The first and second stepped portions 807 aand 807 b deflect the fuel in parallel and upward, and the thusdeflected fuel is directed toward the upstream side of the squish fromthe spark plug 6. The fuel deflected by the first and second steppedportions 807 a and 807 b forms favorable combustible mixtures having athickness larger than that of the above-mentioned embodiments, andmoving toward the spark plug 6 due to the squish. In the presentembodiment, therefore, the combustible mixture stays contacted to thespark plug in the direction of thickness for a relative long period.Therefore, the period in which the combustible mixture is contacted tothe spark plug is lengthened compared to that of the prior art, and theignition performance is reliably ensured at the ignition timing.

[0098] In the present embodiment, when the amount of injected fuelincreases on the high engine load side, the fuel also collides with thethird stepped portion 807 c and is deflected upward. The combustiblemixture formed by this fuel is located neighboring the combustiblemixture formed by the fuel deflected upward by the second steppedportion 807 b, contributing to further increase the thickness of thecombustible mixture, to lengthen the period in which the combustiblemixture moving in the direction of thickness stays contacted to thespark plug, and to more reliably ensure the ignition performance at theignition timing.

[0099]FIG. 19 shows a fuel injection pattern and illustrates the directcylinder injection-type spark ignition internal combustion engineaccording to a fourteenth embodiment of the present invention. In FIG.19, a dotted line represents a conventional fuel injection pattern and asolid line represents a fuel injection pattern according to the presentembodiment in which the injection rate is increased in an early stage offuel injection and is decreased in a last stage of fuel injection. Thismakes it possible to inject the fuel in the same amount within the sameinjection period. As the injection rate is decreased in the last stageof fuel injection, the fuel injected at this moment possesses adecreased amount of kinetic energy making it possible to extend theperiod until the combustible mixture arrives at the spark plug from whenit was injected. This, in other words, lengthens the whole length of thecombustible mixture, and the combustible mixture stays contacted to thespark plug for an extended period making it possible to reliably ensurethe ignition performance at the ignition timing.

[0100] In the present embodiment, it is also possible not to increasethe injection rate in the early stage of fuel injection. Accordingly,the period of fuel injection is extended. When the injection rate isdecreased, the fuel is easily vaporized to form a combustible mixture,i.e., the combustible mixture is formed at an early time. Despite thefuel injection end timing is retarded, therefore, the injected fuel isall forming the combustible mixture at the ignition timing and noproblem arouses. This means that the fuel can be injected in a furtherincreased amount if the injection rate is increased in the early stageof fuel injection.

[0101] Despite the injection rate is increased in the early stage offuel injection, the fuel injected at this moment forms a favorablecombustible mixture over a sufficiently long period until the ignitiontiming. The fuel injection valve is generally so constructed that theinjection rate varies depending upon the amount of lifting the needlevalve. To decrease the injection rate in the last stage of fuelinjection, therefore, the lifting amount of the needle valve may bedecreased in the last stage of fuel injection. Moreover, the fuelinjection valve generally injects fuel of a high pressure via a fuelreservoir of a small capacity. While the fuel injection valve is beingopened, therefore, the fuel is fed to the fuel reservoir through thefuel feed passage. If the fuel feed passage is provided with a choke,therefore, fuel of a high pressure in the fuel reservoir is injected inthe early stage of fuel injection. In the last stage of fuel injection,however, the pressure of fuel in the fuel reservoir decreases, and theinjection rate decreases.

[0102]FIG. 20 is a diagram schematically showing a crank mechanism forillustrating the direct cylinder injection-type spark ignition internalcombustion engine according to a fifteenth embodiment of the presentinvention, wherein the crank mechanism 900 of the present embodimentrevolves in the clockwise direction, and the center 900 a of revolutionis deviated toward the left with respect to the center axis of a piston508. Therefore, though the angular velocity of the crank is high whenthe piston 508 descends, the angular speed of the crank is low when thepiston 508 ascends. In the present embodiment, the period in which thecombustible mixture stays contacted to the spark plug is not extended.Despite the fuel injection timing being deviated to some extent in thecompression stroke, however, the rising speed of the piston is slow sothat the fuel can be injected at nearly a desired position of thepiston, making it possible to reliably ensure the ignition performance.

[0103] According to the above-mentioned fourteenth embodiment, theinternal combustion engine is not limited to the one in which the fuelis deflected toward the spark plug by the cavity in the top surface ofthe piston, but may be the one in which the fuel is vaporized while itis flying and is directly headed toward the spark plug, to extend theperiod in which the combustible mixture stays contacted to the sparkplug compared to that of the prior art and to ensure reliable ignitionperformance. According to the fourteenth and fifteenth embodiments, theengine is not limited to the one in which the fuel is injected in nearlythe shape of a fan, but may be the one in which the fuel is injected ina conical shape. These internal combustion engines, too, make itpossible to ensure more reliable ignition performance than that of theprior art.

[0104] Although the invention has been described with reference tospecific embodiments thereof, it should be apparent that numerousmodification can be made thereto by these skilled in the art, withoutdeparting from the basic concept and scope of the invention.

What is claimed is:
 1. A direct cylinder injection-type spark ignitioninternal combustion engine comprising a spark plug, a cavity formed inthe top surface of a piston, and a fuel injection valve for injectingfuel in nearly the shape of a fan having a relatively small thickness sothat the fuel collides with a bottom wall of said cavity at an acuteangle, wherein, when the fuel injected in nearly the shape of a fan fromsaid fuel injection valve is considered by being divided into aplurality of fuel segments in a radial direction, the bottom wall ofsaid cavity has a plurality of neighboring fuel leading passages forleading said plurality of fuel segments collided toward the side wall ofsaid cavity, the side wall of said cavity has a first fuel deflectionpassage and a second fuel deflection passage for so deflecting at leasttwo of said plurality of fuel segments led by said plurality of fuelleading passages as to pass near said spark plug, and the depth near theside wall of said cavity in a first fuel leading passage among saidplurality of fuel leading passages for leading the fuel segment to saidfirst deflection passage, is smaller than the depth near the side wallof said cavity in a second fuel leading passage among said plurality offuel leading passage among said plurality of fuel leading passages forleading said fuel segment to said second fuel deflection passage.
 2. Adirect cylinder injection-type spark ignition internal combustion engineaccording to claim 1, wherein the side wall of said cavity has aplurality of fuel deflection passages for so deflecting all of said fuelsegments other than said two fuel segments as to pass near said sparkplug, the depth near the side wall of said cavity in said first fuelleading passage is the smallest, and the depths near the side wall ofsaid cavity in said neighboring fuel leading passages gradually change.3. A direct cylinder injection-type spark ignition internal combustionengine according to claim 1, wherein said first fuel leading passage iscloser to said spark plug than said other fuel leading passages.